Stabilization of synergistically sensitized photographic systems



United States Patent 3 420,670 STABILIZATION OF SYNERGISTICALLY SENSI- TIZED PHOTOGRAPHIC SYSTEMS Kirby M. Milton, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey N0 Drawing. Filed Nov. 26, 1965, Ser. No. 510,054 US. Cl. 96-409 11 Claims Int. Cl. G03c 1/34; G03c 1/34 This invention relates to photography and more particularly to the stabilization of photographic silver halide emulsions sensitized with a combination of noble metal sensitizer and a labile selenium sensitizer.

In copending application, Ser. No. 468,972 filed July 1, 1965, now U.S. Patent 3,297,446, of Joseph S. Dunn, it is shown that small amounts of selenium sensitizers can be employed in combination with noble metal sensitizers to produce sensitizing effects for photographic systems such as silver halide emulsions which cannot be obtained with a combination of sulfur sensitizer and noble metal sensitizer, even where a considerably larger amount of sulfur sensitizer than selenium sensitizer is employed. While such Dunn sensitizing combinations do produce marked increases in speed, as compared with goldand sulfur-sensitizer combinations, they introduce fog or stability problems, particularly with high chloride-content silver halide emulsions.

It is, therefore, an object of my invention to provide new stabilized photographic silver halide emulsions containing a combination of a labile selenium sensitizer and a noble metal sensitizer for increasing the speed synergistically of such photographic systems.

It is another object of this invention to provide new stabilized synergistically sensitized silver halide emulsions without adversely affecting the speed of such emulsions.

It is likewise an object of this invention to provide a new method for reducing sensitization fog of high chloride-content silver halide emulsions sensitized with a combination of a gold salt and a labile selenium sensitizer.

Other objects will become apparent from a consideration of the following description and examples.

I have found that the tendency of photographic silver halide emulsions of high chloride content sensitized with sensitizer combinations of noble metal sensitizers and selenium sensitizers to produce fog can be advantageously controlled by including in the silver halide emulsion during the chemical sensitization a 3-pyrazolidone.

A wide variety of 3-pyrazolidones can be used in the silver halide emulsions of the invention. Typical suitable 3-pyrazolidones are disclosed in US. Patent 2,289,367; US. Patent 2,685,516; US. Patent 2,751,297; US Patent 2,772,282; British Patents 679,677 and 679,678; and the Journal of Organic Chemistry, 26, 2803 (1961). Typically such 3-pyrazolidones can be represented by the following formula wherein: R, R R R and R can be alkyl radicals (preferably having 1 to 4 carbon atoms) and including substituted lower radicals such as chloro-substituted alkyl radicals; hydrogen atoms; aryl radicals and including substituted aryl radicals such as phenyl, chlorophenyl, ptolyl, naphthyl and B-hydroxyethylphenyl, and the like; and heterocyclic radicals such as those having at least one hetero atom like sulfur, nitrogen or oxygen. Illustrative 3-pyrazolidones include:

1-phenyl-3 -pyrazolidone 1-phenyl-4-methyl-3-pyrazolidone l-phenyl-4,4-dimethyl-3 -pyrazolidone 1- 4-aminophenyl) -3-pyrazolidone 1-pheny1-4,4-dimethyl-5 ,5 -dimethyl-3 -pyrazolid0ne 1-phenyl-4,4-di-n-butyl-3-pyrazolidone 4-n-butyl-1-phenyl-3-pyrazolidone 1-phenyl-4-o-tolyl-3-pyrazolidone 5 -benzothiazolyl-3-pyrazolidone 1-pyridyl-3 -pyrazolidone 1-m-tolyl-4-phenyl-3 -pyrazolidone 1-thiomorpholino-3-pyrazolidone 1-phenyl-4,4-di-n-propyl-3-pyrazolidone 1-methy1-4,4-dimethyl-5,5-dimethyl-3 -pyrazolidone 4-benzothiazolyl-S-pyrazolidone 1- 7-hydroxy-2-naphthyl -4-methyl-4-n-propyl-3- pyrazolidone 1- o-chlorophenyl -4-methyl-4-ethyl-3-pyrazolidone 1- pfl-hydroxyethyl phenyl] -4,4-dimethyl-3- pyrazolidone l-p-diphenyl-4,4-dimethyl-3-pyrazolidone 1-(p-fi-hydroxyethylphenyl)-3-pyrazolidone 5 -phenyl-3 -pyrazolidone 5-methyl-3-pyrazolidone 1-p-chlorophenyl-3 -pyrazolidone 1-phenyl-5-phenyl-3-pyrazolidone 1-m-tolyl-3 -pyrazolidone 1-phenyl-4-methyl-3-pyrazolidone 1-p-tolyl-5-phenyl-3-pyrazolidone 1-o-tolyl-3-pyrazolidone 1-p-methoXyphenyl-3-pyrazolidone 1-acetamidophenyl-3-pyrazolidone 1-m-aminophenyl-4-methyl-4-propyl-3 -pyrazolidone l-m-acetamidophenyl-4,4-diethyl-3 -pyrazolidone 1-p-methoxyphenyl-4,4-diethyl-3-pyrazolidone 1-p-tolyl-4,4-dimethyl-3 =pyrazolidone 1-benzothiazolyl-3 -pyrazolidone 1-morpholinyl-3 -pyrazolidone The amount of 3-pyrazolidone utilized in preparing the present emulsions can be widely varied, useful concentrations varying with the particular 3-pyrazolidone used, the particular sensitizer utilized, the extent of the sensitization, and related factors. However, I have found that at least about 1 mg. is useful, and more generally 1 to 1000 mg., and preferably 5 to mg., of 3-pyrazolidone per mole of silver halide in the emulsion. The 3- pyrazolidone stabilizers are added to the present emulsions during the sensitization or finishing of the emulsion.

The selenium sensitizers useful in my invention include a wide variety of labile selenium sensitizers, many having been previously suggested for use alone in sensitizing photographic silver halide emulsions. Suitable selenium addenda are disclosed in Sheppard et al. US. Patent 1,623,- 499, issued Apr. 5, 1927, as well as Sheppard US. Patents 1,574,944, issued Mar. 2, 1926, and 1,602,592 issued Oct. 12, 1926. The labile selenium sensitizers of my invention which have been found to be particularly useful are organic selenium compounds wherein the selenium atom is doubly bonded to a carbon atom of the organic compound through a covalent linkage. Thus, especially useful compounds include selenoamides, selenoketones (especially ketones having an alkyl radical attached to the moiety), selenocarboxylic acids and esters, etc. Useful groups of selenium sensitizers include aliphatic selenoureas wherein the aliphatic radical is, for example, an alkyl radical such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, etc. Such selenoureas have at least one hydrogen atom attached to the nitrogen atom thereof, thus making possible the formation of an enol tautomer. Also useful in my invention are analogous selenoureas containing one or more aromatic radicals, such as phenyl, tolyl, etc., or heterocyclic radicals, such as benzothiazolyl, pyridyl, etc., and aliphatic isoselenocyanates. Other useful labile selenium sensitizers are selenophosphates such as tri-alkyl and tri-aryl selenophosphates. It has also been found that colloidal selenium itself is a useful sensitizer.

Illustrative addenda suitable for furnishing the labile selenium moiety in the stabilized silver halide emulsions of the invention include:

Colloidal selenium, Selenoacetone, Selenoacetophenone, Tetramethylselenourea, N-(fi-carboxyethyl)-N,N'-dimethylselenourea, Selenoacetamide, Diethylselenide, Tri-p-tolylselenophosphate, Tri-n-butylselenophosphate, 2-selenopropionic acid, 3-selenobutyric acid, Methyl-3-selenobutyrate, Allyl isoselenocyanate, and Dioctylselenourea.

The concentration of selenium sensitizer can be varied considerably depending upon the particular selenium addendum employed (some sensitizers being more efficacious than others), the nature of the silver halide emulsion, the amount and chemical nature of the noble metal sensitizer, etc. I have found that useful results can be obtained using amounts as small as 0.05 mg. of selenium sensitizer per mole of silver halide although considerably larger amounts can also be employed, such as 5.0 mg. or more per mole of silver halide.

The term labile as used herein has the meaning well understood by those skilled in the art of photography, i.e., a material which yields a silver salt that is insoluble in water at room temperature (20 C.) upon addition to an aqueous silver nitrate solution. For example, selenourea is a labile selenium compound, since silver selenide precipitates when selenourea is added to an aqueous silver nitrate solution. Similarly, colloidal selenium precipitates silver selenide upon addition to aqueous silver nitrate and is, therefore, a labile selenium addendum or sensitizer of invention.

The noble metal sensitizers useful in the photographic systems stabilized in accordance with my invention include the well-known gold sensitizers which have been previously recognized as useful in the photographic art and found to be outstanding in their sensitizing action, including water-soluble and water-insoluble organic and inorganic gold compounds and salts, although other noble metal sensitizers can be used, including palladium, platinum, etc., sensitizers such as are disclosed in Smith et al. U.S. Patent 2,448,060 issued Aug. 31, 1948. Typical suitable gold sensitizers are described in Waller et al. U.S. Patent 2,399,083 issued Apr. 23, 1946, and Damschroder et al. U.S. Patent 2,642,361 issued June 16, 1953.

Illustrative addenda suitable for furnishing the noble metal moiety in the sensitizer combinations of the invention include:

Gold chloride,

Potassium aurate, Potassium auriaurite, Potassium auricya-nide, Potassium aurithiocyanate, Gold sulfide,

Gold selenide,

Gold iodide,

Potassium chloroaurate,

Ethylenediamine-bis-gold chloride,

Ammonium chloroplatinite, i.e., (NH PtCl Ammonium chloropal-ladate, i.e., (NI-LQ PdCI and Organic gold sensitizers such as Compounds I to X described in columns 2 and 3 of U.S. Patent 2,642,361.

The quantity of noble metal sensitizer useful in sensitizing the photographic systems of the invention can likewise be varied as in the case of selenium sensitizers. I have found, for example, that amounts varying from about 0.1 to 25.0 mg. of gold sensitizer per mole of silver halide are quite satisfactory.

The noble metal moiety and the labile selenium moiety used in sensitizing the photographic systems stabilized in accordance with the invention are more generally added to the photographic system as separate entities, although such is not necessary.

It has been found that particularly useful results are obtained in prepared noble metal and selenium sensitizing combinations in cases where a water-soluble thiocyanate compound is present. Typical thiocyanates include sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, etc. Other water-soluble thiocyanates can be employed to equal advantage. The amount of thiocyanate compound used can likewise be varied, depending upon the particular system being sensitized, relative amounts of selenium and noble metal sensitizers, etc.

The sensitizing addenda used in sensitizing the photographic systems stabilized in accordance with the invention can be added in a variety of ways to photographic systems and at various stages in the preparation of such. In general, such addenda can be added with useful effects at the completion of the Ostwald ripening and prior to one or more of the final digestion operations. The sensitizing addenda of the invention are preferably added to silver halide emulsions after the silver halide grains are substantially in their final size and shape. The addenda can be added in the form of their aqueous solutions, where they are soluble in water, or in an innocuous organic solvent where the sensitizer does not have sufficient solubility in water to be used in the form of an aqueous solution. Particularly useful organic solvents include ethanol, methanol, pyridine, acetone, dioxane, etc. That is, organic solvents which have a rather high degree of polarity are preferred. Where it is desired to add the sensitizing addenda in some other form than a solution, this procedure is also possible, especially where the sensitizer is available in the form of a colloidal suspension. In some cases, it is possible to add the sensitizers suspended in an organic solvent which forms very small suspended particles or globules in the photographic emulsion similar to the type of colloidal particle produced in preparing coupler dispersions. Dispersing media useful for this purpose include tricresyl phosphate, dibutyl phthalate, triphenyl phosphate, etc. Especially useful results are obtained where all addenda are added prior to the final digestion. The present 3-pyrazolidone stabilizing addenda are added to the silver halide emulsion to be present during the sensitization with the above-described noble metal and labile selenium sensitizer combinations. Likewise, labile sulfur compounds such as are disclosed in copending McVeigh application Ser. No. 486,235 now U.S. Patent No. 3,297,447 can also be added during the sensitization of the present emulsions.

In the preparation of the silver halide emulsions of the invention, there is employed as the dispersing agent gelatin or some other colloidal hydrophilic material, such as colloidal albumin, a cellulose derivative or a synthetic resin, for instance, a polyvinyl compound, an acrylateacrylic acid copolymer, and the like.

I have found that the speed of noble metal-selenium sensitized silver halide emulsions stabilized with 3-pyrazolidones can be further increased by including in the emulsions a variety of speed-increasing compounds of the quaternary ammonium type of Carroll US. Patent 2,271,- 623, issued Feb. 3, 1942; Carroll and Allen U.S. Patent 2,288,226 issued June 30, 1942; and Carroll and Spence US Patent 2,334,864 issued Nov. 23, 1943; or the polyethylene glycol type of Carroll and Beach US. Patent 2,708,162, issued May 10, 1955; or the quaternary ammonium salts and polyethylene glycols of Piper U .8. Patent 2,886,437, issued May 12, 1959; as well as the thio polymers of Graham and Sagal US. Patent 3,046,129 issued July 24, 1962, and the Dann and Chechak US. Patent 3,046,134 issued July 24, 1962. Frequently, useful effects can be obtained by adding the aforementioned speed-increasing compounds to the photographic developer solutions instead of, or in addition to, the photographic emulsions.

Particularly useful silver halide emulsions sensitized with a noble metal and a labile selenium sensitizer as described above are obtained when a thioether silver halide solvent is present during the grain formation of the silver halide. Typical suitable thioethers include the polythiaalkylenediols described in Williams and Cossar US. Patent 3,021,215, issued Feb. 13, 1962, and in Dann and Gates US. Patent 3,062,646, issued Nov. 6, 1962.

The feature 3-pyrazolidone stabilizing agents have particular utility for stabilizing noble metal and selenium sensitized silver halide emulsions having at least 50 mole percent chloride as the halide moiety. Suitable silver halide emulsions include silver chloride, silver chlorobromide, silver chloroiodide and silver chlorobromoiodide. The present invention is particularly directed to stabilizing high contrast or graphic arts-type of silver halide emulsions. However, the present emulsions are also useful in X-ray and other nonspectrally sensitized systems, as well as in orthochromatic, panchromatic and infrared systems, The subject emulsions can be utilized in conventional color photographic systems such as in color diffusion transfer system using dye developers or couplers that form diffusible dyes, dye bleach systems, color systems utilizing couplers or color formers in processing compositions or incorporated in the emulsion, and related we'll-known color systems.

The invention is further illustrated by the following examples of preferred embodiments thereof.

Example 1 One mole of a high contrast, graphic arts-type gelatino silver chlorobromoiodide emulsion comprising 90 mole percent chloride and 9 mole percent bromide and 1 mole percent iodide was treated with 1.72 mg. of potassium chloroaurate, 1.33 mg. of N,N-dimethylselenourea and 4 methyl-l-phenyl-3-pyrazolidone as an antifoggant at the concentrations set out in Table I below. The emulsions were heated for 60 minutes at 65 C., cooled and coated on a cellulose acetate film support at a coverage of 477 mg. silver and 473 mg. gelatin per square foot. A second mole of the same emulsion was similarly treated in the absence of the 4-methyl-l-phenyl-3-pyrazolidone antifoggant. The coated film samples were exposed on an Eastman type IB sensitometer and processed for 4 minutes in Kodak D11 developer at 72 F., followed by fixing in hypo, washing and drying in the usual manner. The results are summarized in Table I below.

Example 2 An emulsion similar to that described in Example 1 was prepared except that 50 mg. per mole of silver halide of l-phenyl-4,4-dimethyl-3-pyrazolidone was utilized in lieu of the 4-inethyl-l-phenyl-3-pyrazolidone during the sensitization with the gold and selenium salts. The emulsion was coated, exposed and processed as described in Example 1. A fog level substantially below that of a similar emulsion sensitized in the absence of a 3-pyrazolidone was obtained.

Example 3 One mole of an emulsion similar to that in Example 1 was sensitized with 9.7 mg. gold sulfide and 0.89 mg. N,N-dimethylselenourea, in lieu of the sensitizing salts and concentrations described in Example 1, in the presence of 15 mg. 4-methyl-1-phenyl-3-pyrazolidone. The emulsion was heated as indicated in Table II below, cooled and the various samples were coated as in Example 1. A second mole of the same emulsion was similarly treated in the absence of 4-methyl-l-phenyl-3-pyrazolidone. The resulting emulsions were coated, exposed and processed as described in Example 1. The results are summarized in Table II below.

TABLE II 4 D-19 Feature addendum Heating time and temp. Rel. Fog

Speed 1 100 .10 0, 65 C. 151 .14 10, 65 C. 159 .11 20', 65 C. 174 1O 30', 65 C. 159 .09 40, 65 C. 151 .12 100 .05 0, 65 C. 166 08 10, 65 C. 166 .08 20 65 C. 174 07 166 .07 166 .08

The speed of the control without heat treatment was set equal to 100 upon development in the D-19.

2 No heat treatment.

As can be observed from the data in Table II, the 3- pyrazolidone effectively controlled the fog level during sensitization.

The relative ineffectiveness of the subject 3-pyrazolidones to stabilize low chloride-content gold and selenium sensitized silver halide emulsions is illustrated in Example 4 below, and the relative ineffectiveness of several conventional silver halide developing agents to stabilize gold and selenium sensitized silver halide emulsions is illustrated in Example 5 below.

Example 4 To one mole of a medium grain gelatino silver bromoiodide mole percent bromide and 5 mole percent chloride) emulsion was added 2.6 mg. of potassium chloroaurate, mg. of sodium thiocyanate and 1.06 mg. of N,N-dimethylselenourea. The emulsion was then split into two portions. One portion was retained as a control. To the remaining portion was added 15 mg. 4- methyl-l-phenyl-3-pyrazolidone per silver mole. Both portions were then digested at 65 C. to obtain optimum speed therein, then coated on a cellulose acetate film support to yield a silver coverage of 540 mg. per square foot and a gelatin coverage of 725 mg. per square foot. Samples of each of these coatings were exposed on an Eastman type IB sensitometer, processed for 5 minutes in Kodak DK-5O developer, fixed in hypo, washed and dried in the usual manner. The results are sumarized in Table III below.

TABLE III Similar results were obtained with a gelatino silver 'halide emulsion comprising 40 mole percent chloride and 60 mole percent bromide.

Example 5 To one mole of a gelatino silver halide emulsion of the type described in Example 1 was added 0.89 mg. of N,N- dimethylselenourea, and 7.7 mg. gold sulfide. The emulsion Was then split into four parts and further treated as follows:

Part 1: No further addition. Control Part 2: To this portion was added 553 mg. resorcinol/ silver mole Part 3: To this portion was added 50mg. hydroquinone/ silver mole Part 4: To this portion was added 50 mg. N-methyl-paminophenol sulfate/silver mole Each of these portions was then digested at 65 C. for the times listed in Table IV below to obtain the optimum speed-fog values in each case. The emulsion samples were then coated, exposed and processed as described in Example 1 except that both Kodak D-ll and Kodak D-19 developers were used to yield the following data:

TABLE IV Digestion 4 D-19 Emulsion time at 4 D-l1/ 65 C. Rel. 'y Fog Fog Speed The developers referred to in the above examples are described in Processing Chemicals and Formulas for Black-and-White Photography, Sixth Edition, 1963, a publication of Eastman Kodak Company, Rochester, New York.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. In a photographic silver halide emulsion wherein said halide comprises at least 50 mole percent chloride sensitized with a noble metal and labile selenium, the improvement wherein a 3-pyrazolidone is used as a stabilizer during the sensitization of said emulsion.

2. A photographic silver halide emulsion as described in claim 1 wherein the noble metal sensitizer is a gold salt.

3. A photographic silver halide emulsion as described in claim 1 wherein the silver halide is dispersed in gelatin.

4. A photographic silver halide emulsion as described in claim 1 wherein the 3-pyrazolidone has the formula wherein each R substituent is selected from the group consisting of a hydrogen atom, an alkyl radical, an aryl radical and a heterocyclic radical containing at least one hetero atom selected from the group consisting of sulfur, nitrogen and oxygen.

5. A photographic silver halide emulsion as described in claim 1 wherein the noble metal sensitizer is potassium chloroaurate.

6. A photographic silver halide emulsion as described in claim 1 wherein the noble metal sensitizer is gold sulfide.

7. A photographic silver halide emulsion as described in claim 1 wherein the labile selenium sensitizer is N,N-di methylselenourea.

8. A photographic silver halide emulsion as described in claim 1 wherein the 3-pyrazolidone is 4-methyl-1- phenyl-3-pyrazolidone.

9. A photographic silver halide emulsion as described in claim 1 wherein the 3-pyrazolidone is 1-phenyl-4,4-dimethyl-3-pyrazolidone.

10. A photographic silver halide emulsion as described in claim 1 wherein the 3-pyrazolid0ne is utilized at a concentration of about 1 to 1000 mg. per mole of silver halide.

11. In a photographic gelatino silver halide emulsion wherein said halide comprises at least 50 mole percent chloride sensitized with a gold salt and labile selenium, the improvement wherein a stabilizer is used during the sensitization of said emulsion, said stabilizer being about 1 to 1000 mg. per mole of said silver halide of a 3-pyrazolidone having the formula References Cited UNITED STATES PATENTS 2/1963 Willems et a1 96-109 X 1/1967 McVeigh 96-109 NORMAN G. TORCHIN, Primary Examiner.

R. E. FICHTER, Assistant Examiner.

US. Cl. X.R. 96-107 

1. IN A PHOTOGRAPHIC SILVER HALIDE EMULSION WHEREIN SAID HALIDE COMPRISES AT LEAST 50 MOLE PERCENT CHLORIDE SENSITIZED WITH A NOBLE METAL AND LABILE SELENIUM, THE IMPROVEMENT WHEREIN A 3-PYRAZOLIDONE IS USED AS A STABILIZER DURING THE SENSITIZATION OF SAID EMULSION. 